Date comparison goes wrong

Question

So I have this code that compares a date to today’s date, but sometimes the dates are as follows: :

   D/tag: Sat Jul 22 00:00:00 GMT+01:00 2017 <<-Data indicada
   D/tag: Sat Jul 22 18:57:17 GMT+01:00 2017 <<-Data de hoje

And I want that by doing this, the program does not return that the date indicated is shorter or is an earlier date than today, I want if today’s date is indicated as not being earlier than today’s date. My code that compares is as follows :

  if(teste!=null){
            caldroidFragment.setBackgroundDrawableForDate(cyan, teste);
            DatesList.add(teste);
            int ListSize = DatesList.size();
             if(cal.getTime().compareTo(teste)>0){
                 caldroidFragment.setBackgroundDrawableForDate(red, teste);
             }
        }

He in this example I indicated this to return 1. Cal.getTime() is the present time. "test" is the date indicated by the user.

My code is this: :

    for(int i=1;i <= myDB.getLastId();i++){

        cal.set(Calendar.HOUR_OF_DAY,0);
        cal.set(Calendar.MINUTE,0);
        cal.set(Calendar.SECOND,0);

        String dt = myDB.getDates(i);
            java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("dd-MM-yyyy");
            Date teste = null;

            try {
                teste = sdf.parse(dt);
            } catch (ParseException e) {
                e.printStackTrace();
            }
        if(teste!=null){
            Log.d(Tag,""+teste);
            Log.d(Tag,""+cal.getTime());
            Log.d(Tag,""+cal.getTime().compareTo(teste));
            caldroidFragment.setBackgroundDrawableForDate(cyan, teste);
            DatesList.add(teste);
            int ListSize = DatesList.size();
             if(cal.getTime().compareTo(teste)>0){
                 caldroidFragment.setBackgroundDrawableForDate(red, teste);
             }
             else if(cal.getTime().compareTo(teste)==0){
                 caldroidFragment.setBackgroundDrawableForDate(white,teste);
             }
        }



    }

The log is giving :

    Sat Jul 22 00:00:00 GMT+01:00 2017
    Sat Jul 22 00:00:00 GMT+01:00 2017
    1

I don’t understand why cal.getTime(). compareTo(test) is returning 1 when the values are clearly equal! Thank you

Answer 1

When you compare two objects of the type Date, in fact you’re comparing the millisecond representation of these objects.

The method Date.compareTo(Date anotherDate) is implemented as follows:

public int compareTo(Date anotherDate) {
    long thisTime = getMillisOf(this);
    long anotherTime = getMillisOf(anotherDate);
    return (thisTime<anotherTime ? -1 : (thisTime==anotherTime ? 0 : 1));
}

Notice that he calls getMillisOf makes the comparison using the millisecond representation of the two objects Date.

---

On the line Log.d(Tag,""+cal.getTime());, you printa on console a Date format EEE MMM dd HH:mm:ss zzz yyyy

Note that in the format, the milliseconds field is ignored. So when you printou the Date, you weren’t seeing your full representation.

---

To solve your problem you can:

Reset minutes, seconds and milliseconds fields of the two calendars (easiest).

cal.set(Calendar.HOUR_OF_DAY, 0);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);

Note that, how you created the date teste with sdf.parse(dt) passing only dd-MM-yyyy, the time, minute and millisecond fields will already be zero.

Thus, the verification cal.getTime().compareTo(teste)>0 should work.

Compare each object field Calendar (more laborious)

if(teste!=null){
    Calendar testeCal = Calendar.getInstance();
    testeCal.setTime(teste);

    caldroidFragment.setBackgroundDrawableForDate(cyan, teste);
    DatesList.add(teste);
    int ListSize = DatesList.size();

    if(cal.get(Calendar.DAY_OF_MONTH) == testeCal.get(Calendar.DAY_OF_MONTH) &&
        cal.get(Calendar.MONTH) == testeCal.get(Calendar.MONTH) &&
        cal.get(Calendar.YEAR) == testeCal.get(Calendar.YEAR)) {
        ...
    }

}

This approach also works, but it becomes more laborious to make comparisons of larger or smaller dates.